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PubMed2006

[Cytogenetics and in vitro drug resistance of acute leukemia in children and adults].

In spite of continuous progress in the therapy of acute leukemia, relapses still occur frequently both in children and adults. The presence of cytogenetic aberrations in leukemic cells at presentation is an important prognostic factor in acute leukemia. The translocation t(9;22) and the 11q23/MLL rearrangement are related to poor prognosis, while hyperdiploidy >50 chromosomes and the translocation t(12;21) are indicators of good prognosis in acute lymphoblastic leukemia (ALL). In acute myeloid leukemia (AML), t(8;21), t(15;17), and inv(16) indicate good prognosis, whereas 5/5q-, 7/7q-, and complex karyotype indicate poor prognosis. It seems that the prognostic value of cytogenetic changes is related to differences in cellular drug resistance in ALL and, to lesser extent, in AML. Genetic profiling based on microarray analysis confirms the correlation between cytogenetic changes in leukemic cells and drug resistance in ALL. The cytogenetic profile possibly determines cellular drug resistance and final therapy outcome. Knowledge on the karyotype-related drug resistance profile might enable the use of targeted therapy in resistant/refractory acute leukemia both in children and adults.

Adult↗
PubMed2000

An assessment of the use of interphase FISH with chromosome specific probes as an alternative to cytogenetics in prenatal diagnosis.

We have assessed the effects that would have been observed if we had changed from standard prenatal diagnosis to interphase fluorescence in situ hybridization (FISH) on our amniocentesis samples. We aimed to estimate the number of cases with aberrations other than chromosomes 13, 18, 21, X and Y, which would not have been detectable by FISH and to assess the potential clinical implications for these cases. In 1687 prenatal diagnoses, 111 cases had abnormal cytogenetic reports (6.5% aneuploidy rate). Out of those 111 cases, 14 had chromosomal abnormalities not detectable by FISH but four of these had major structural abnormalities diagnosed on ultrasound, which would have lead to counselling of a very poor prognosis anyway. In 10 cases without abnormal ultrasound findings, if FISH had been used rather than cytogenetics, it appears that there may have had no detrimental effects on the clinical outcomes of the cases studied. Out of those 10 cases, two pregnancies were terminated because of abnormal cytogenetic results (one was due to maternal age and the second one was due to abnormal biochemical screening) (mosaic 46,XY, /47,XY,+mar and 46,X,del(8)(p21) respectively) and their post-mortem results also did not show any abnormalities. One pregnancy was continued in spite of a de novo chromosomal rearrangement and resulted in an apparently normal live birth. Five cases (including a set of twins) with inherited balanced translocations resulted in four normal live births and one unexplained intrauterine death at 32 weeks' gestation and post-mortem was declined. One case with a paternally derived abnormal chromosome 21, decided to continue the pregnancy and resulted in a normal live birth. The last case in this group resulted in a rhesus related intrauterine death in the second trimester, and although an abnormal chromosome 13 insertion (paternally derived known aberration) there was no abnormality found at post-mortem. Therefore, we suggest that it is reasonable to use FISH as an alternative prenatal diagnosis for indications such as advanced maternal age and abnormal maternal serum biochemical screening when high quality ultrasound scanning is performed, but FISH should only be used as an additional test to conventional cytogenetics for the other indications, especially when abnormalities are found on ultrasound scan.

Adult↗
PubMed1993

Hematologic remission and cytogenetic improvement after treatment of stable-phase chronic myelogenous leukemia with continuous infusion of low-dose cytarabine.

Prolonged exposure to low concentrations of cytarabine preferentially inhibits in vitro growth of neoplastic myeloid progenitors from patients with chronic myelogenous leukemia (CML) compared to that of normal myeloid progenitors. Continuous infusions of cytarabine in doses of 15-30 mg/m2/day were therefore administered for extended periods to patients with CML in stable phase to determine if this treatment could achieve selective cytoreduction of Philadelphia chromosome (Ph)-positive cells. Five patients demonstrating > 90% Ph-positive metaphases before treatment received a total of 43 cycles of cytarabine infusional therapy. Cytarabine was administered on an outpatient basis using a portable, battery-operated syringe pump until the total leukocyte count reached 2500/microliters or the platelet count reached 75,000/microliters. A new cycle was begun when the total leukocyte count exceeded 4,000/microliters and the platelet count exceeded 100,000/microliters. The median duration of cytarabine administration per cycle was 29 days (range 15-72 days). Leukocytosis was readily controlled by low-dose cytarabine therapy in all patients. All five patients experienced complete hematologic responses during cytarabine therapy. The fraction of Ph-positive metaphases in the marrow of the five patients was reduced to 0, 10%, 43%, 72%, and 84%, respectively, during therapy. The median time to achieve optimal cytogenetic response was 4.8 months (range 2.8-8.6 months). One patient demonstrated a complete cytogenetic response after three cycles of cytarabine. Another patient demonstrated persistent cytogenetic improvement during 20 cycles of cytarabine, with a median 38% Ph-positive marrow metaphases (range 10-53%) over 32 months. Cytarabine therapy was generally well-tolerated, but was discontinued in one patient because of persistent asymptomatic elevations in hepatic enzymes, which resolved within 2 months after discontinuing therapy. There were no episodes of fever during neutropenia, and platelet transfusions were not required. However, symptomatic anemia requiring transfusion of red cells occurred during most cycles of treatment. In summary, treatment of CML with low-dose cytarabine can induce prolonged cytogenetic improvement in some patients with acceptable toxicity. Further evaluation is needed to ascertain the effect of this treatment on duration of stable phase and overall survival.

Adult↗
PubMedDate not supplied

Factors which contribute to cytogenetic frequency of expression in families of fragile X females.

Frequency of expression in mentally retarded (MR) fragile X (fra[X]) males has been shown to be affected by genetic factors and laboratory procedures. Among MR females, factors that contribute to cytogenetic expression have been more problematic in part due to lower frequency of expression and X-inactivation. We examined fra(X) sisters to determine whether genetic factors affecting frequency of expression in sisters were comparable to those in brothers. Evaluations obtained from 2 data sets for a total of 66 families in which at least 2 affected brothers and/or 2 affected sisters were found cytogenetically positive were selected. Of 166 subjects chosen, 118 were male and 48 were female. Sibs were evaluated using an analysis of covariance (ANCOVA) with 2 factors (family, sex) adjusted for the covariate, age. Results indicated that interactive effects (family-by-sex) and main effects (family, sex, age) were significant but the interactive effect of age-by-sex was not. Consequently, one-way analyses of variance (ANOVA) of the effect of family were calculated separately for brothers and sisters. Correlation coefficients between family and cytogenetic frequency was r = .84 for brothers and r = .79 for sisters. Analysis of these coefficients indicated that they were not significantly different from one another (Z = 0.85, p greater than .40). While other factors may affect cytogenetic expression, whatever familial factors control frequency of expression among brothers appear to affect frequency of expression among sisters as well.

Aging↗
PubMed2003

Characterization of a supernumerary ring chromosome 1 mosaicism in two cell systems by molecular cytogenetic techniques and review of the literature.

We report on a 4-year-old boy with developmental delay and microcephaly with an additional small marker chromosome derived from chromosome 1 and detected in 14% of T-lymphocytes by conventional cytogenetics and in 9% of buccal smear cells by interphase FISH. Using molecular cytogenetic techniques, the marker chromosome was characterized as an extra ring chromosome consisting of euchromatic material from the proximal short arm of chromosome 1. We compare the cytogenetic data and the phenotype of our patient to those previously described cases with marker chromosome 1 mosaicism. We conclude that in addition to the straightforward molecular cytogenetic characterization of the euchromatic content of the ring chromosome, the investigation of a second cell system gives additional information about the tissue specific distribution of the supernumerary marker chromosome (SMC) and provides more reliable data for further karyotype/phenotype correlations and the prediction of the phenotypic outcome in prenatal cases.

Child, Preschool↗
PubMed2002

Malignant placental site trophoblastic tumor: a cytogenetic study using comparative genomic hybridization and chromosome in situ hybridization.

BACKGROUND: Placental site trophoblastic tumor (PSTT) is a rare form of gestational trophoblastic neoplasm composed predominantly of intermediate trophoblast. Most showed benign behavior whereas 10-15% of PSTTs were clinically malignant with later recurrence and metastasis. Currently, there are no reliable means to predict clinical outcome, and cytogenetic information is scanty. METHODS: The clinicopathologic features of two cases of malignant PSTT were analyzed. Cytogenetic analysis was performed by comparative genomic hybridization (CGH) and chromosome in situ hybridization (CISH) using frozen tissue and paraffin embedded sections, respectively. RESULTS: Both patients were 32 years old at time of diagnosis. One patient with PSTT presented with menorrhagia, and the other presented with symptoms of missed abortion. Elevated serum human chorionic gonadotropin (HCG) was detected in both patients. Histologic examination showed the typical features of PSTT with high mitotic count (> 5/10 high-power fields). Ovarian and lung metastasis occurred in both patients. Immunohistochemical staining revealed an equal distribution of HCG and human placental lactogen. Cytogenetic studies by CISH showed that karyotypes of these two malignant PSTTs were diploid. Analysis of the tumor tissue by CGH did not show any changes in DNA copy numbers. CONCLUSIONS: The authors' study indicated that the two metastasizing PSTTs had balanced diploid karyotype. The malignant behavior of PSTTs may be not related to the DNA copy number changes. Such cytogenetic study may be useful in distinguishing metastatic PSTT from choriocarcinoma.

Adult↗
PubMed2002

Distinct cytogenetic pathways of advanced-stage neuroblastoma tumors, detected by spectral karyotyping.

Molecular studies of advanced-stage neuroblastoma (NBL) have revealed a marked genetic heterogeneity. In addition to MYCN amplification and chromosome 1 short-arm deletions/translocations detected by conventional cytogenetics, application of fluorescence in situ hybridization has disclosed a high prevalence of 17q gain, whereas allelotyping and comparative genomic hybridization techniques also have revealed loss of 11q and of other chromosomal material. Using the recently developed technique of spectral karyotyping (SKY), we sought to refine the cytogenetic information, identify hidden recurrent structural chromosomal abnormalities, and compare them to the molecular findings. Thirteen samples of metaphase spreads from 11 patients with advanced-stage NBL were analyzed by SKY. Most of them were found to have complex karyotypes (more than three changes per metaphase) and complex unbalanced rearrangements. Recurrent aberrations leading to 17q gain, deletion of 1p, MYCN amplification, and loss of 11q appeared in 7, 4, 4, and 5 patients, respectively, in simple and complex karyotypes. Chromosome 3 changes and gain of 1q and 7q appeared in 6, 5, and 4 patients, respectively, in complex karyotypes only, reflecting later changes. A strikingly high prevalence of the unbalanced translocation der(11)t(11;17), leading to concomitant 11q loss and 17q gain in 4 patients, delineated a distinct cytogenetic group, none having 1p deletion and/or MYCN amplification. der(11)t(11;17) was associated with complex karyotypes with changes in chromosomes 3 and 7q. The 17q translocations with partners other than 11q were associated with 1p deletion and/or MYCN amplification. The distinct cytogenetic subgroups identified by SKY confirm and extend the recent molecular observations, and suggest that different genes may interact in the der(11)t(11;17) pathway of NBL development and progression.

Adolescent↗
PubMed2002

Identification of cytogenetic subclasses and recurring chromosomal aberrations in AML and MDS with complex karyotypes using M-FISH.

Complex chromosomal aberrations (CCAs) can be detected in a substantial proportion of AML and MDS patients, de novo as well as secondary or therapy-related, and are associated with an adverse prognosis. Comprehensive analysis of the chromosomal rearrangements in these complex karyotypes has been hampered by the limitations of conventional cytogenetics. As a result, our knowledge concerning the cytogenetics of these malignancies is sparse. Here we describe a multiplex-FISH (M-FISH) study of CCAs in 36 patients with AML and MDS. M-FISH generated a genome-wide analysis of chromosomal aberrations in CCAs, establishing several cytogenetic subgroups. -5/5q- was demonstrated in the majority of patients (86%). Other rearrangements (present with or without -5/5q-) included: deletion of 7q (47%), 3q rearrangements (19%), and MLL copy gain or amplification (17%). These genetic subgroups seem to display biological heterogeneity: MLL copy gain or amplification in association with 5q- was detected only in AML patients and was significantly associated with extremely short survival (median overall survival: 30 days, P = 0.0102). A partially cryptic t(4;5)(q31;q31), a balanced t(1;8)(p31;q22), and an unbalanced der(7)t(7;14)(q21;q13) were detected as possible new recurrent rearrangements in association with CCAs. Novel reciprocal translocations included t(5;11)(q33;p15)del(5)(q13q31) and t(3;6)(q26;q25). We conclude that AML and MDS with CCAs can be subdivided into molecular cytogenetic subclasses, which could reflect different clinical behavior and prognosis, and that three recurrent chromosomal aberrations are associated with karyotype complexity.

Acute Disease↗
PubMed1994

Rhabdoid tumor of the kidney with primitive neuroectodermal tumor of the central nervous system: associated tumors with different histologic, cytogenetic, and molecular findings.

Rhabdoid tumor of the kidney (RTK) is associated with tumors of the central nervous system (CNS) in approximately 15% of cases. We describe the clinical features, histologic and cytogenetic findings, and molecular analysis of renal and CNS tumors from the same patient. The histology of the renal tumor was consistent with rhabdoid tumor. The CNS tumor was a primitive neuroectodermal tumor (PNET). The karyotype of the RTK was normal male. The PNET of the brain demonstrated monosomy 22 as the only cytogenetic abnormality, similar to reported cases of malignant rhabdoid tumor of the brain, but dissimilar to nonrandom cytogenetic findings in other CNS PNETs. Molecular cytogenetic and DNA marker studies confirmed loss of chromosome 22 in this patient's brain tumor. DNA allelotyping showed retention of both parental chromosome 22 alleles in the RTK and loss of the maternal allele in the PNET. Evaluation of additional RTKs and brain tumors occurring in the same patient may provide insight into the origins and relationships of these enigmatic tumors.

Brain Neoplasms↗
PubMed1995

DNA index and %S-phase cells determined in acute lymphoblastic leukemia of children: a report from studies ALL V, ALL VI, and ALL VII (1979-1991) of the Dutch Childhood Leukemia Study Group and The Netherlands Workgroup on Cancer Genetics and Cytogenetics.

DNA per cell content was routinely recorded by single-parameter flow cytometry in leukemic blasts from 473 children with acute lymphoblastic leukemia (ALL), enrolled in national studies ALL V, VI, and VII (1979-1991) of the Dutch Childhood Leukemia Study Group. The parameters bonemarrow %S-value and DNA Index were compared with clinical features, with chromosome number based on cytogenetic analyses and with treatment results in study ALL VI. %S-values, ranging between 1 and 36%, were unrelated to initial white blood cell count, immunophenotype, and DNA index but were lowest in blasts with L1 morphology. In study ALL VI (non-high risk), the survival of patients with < or = 6% S-phase cells was superior to that of patients with %S-values of > 6 (P = 0.030). Hyperdiploidy, defined by a DNA index > or = 1.16, was compared to the cytogenetic hyperdiploid classification of n > 50. Initially there were 25 discrepancies in 189 samples jointly analysed by flow cytometry and cytogenetics. After review only five discrepancies remained unresolved. Hyperdiploidy, independent of the method used, was found to be unrelated to blast morphology and %S-phase cells but closely associated with c-ALL and was absent in T-ALL. In study ALL VI, event-free survival at 8 years of hyperdiploid patients was 90.6% but was not significantly different from non-hyperdiploid patients (EFS = 82.1%; P = 0.08). Routine DNA flow cytometry appeared a valuable adjunct to cytogenetic analyses and allowed the identification of a large subset of non-high-risk ALL patients in study ALL VI with a DNA index > or = 1.16 or %S-value of < or = 6.0 with highest survival probability.

Bone Marrow↗
PubMed2002

Prenatal diagnosis of 45,X and 45,X mosaicism: the need for thorough cytogenetic and clinical evaluations.

OBJECTIVES: Mosaicism involving a 45,X cell line is relatively common in prenatal diagnosis. In prenatally diagnosed cases, the prognosis of non-mosaic 45,X and 45,X/46,XY mosaicism are different. Therefore, accurate identification of a cell line containing Y chromosome is critical for genetic counseling and postnatal management. METHODS: We investigated the ultrasound findings and outcomes of pregnancies with a 45,X cell line identified during mid-trimester cytogenetic analysis. RESULTS: A total of 105 cases were found to have a 45,X cell line by standard cytogenetic analysis. Seventy-four cases were found to have non-mosaic 45,X at initial diagnosis. Of these 74 cases, 68 had abnormal ultrasound findings that were characteristic of Turner syndrome. Of the six cases with normal ultrasound findings, ultrasound examination was normal with male genitalia identified in three cases. Thorough cytogenetic and fluorescent in situ hybridization (FISH) analysis identified Y chromosome material in all three cases, one with a dicentric Y;14 chromosome and the other two cases with a marker chromosome containing Sex-determining Region (SRY) material in a small portion of the cells. In contrast, in 31 cases with a mosaic 45,X karyotype, ultrasound abnormality was identified only in one case. CONCLUSIONS: The present data suggest the need for follow-up ultrasound examination and thorough cytogenetic and molecular analysis for Y chromosome material in 45,X cases with normal ultrasound findings.

Adult↗
PubMed1996

The contribution of cytogenetics to the histogenesis of meningeal hemangiopericytoma.

Some controversy has existed regarding the nosology of meningeal hemangiopericytoma. In the WHO's classification of 1979 these tumours were included as a subgroup of meningiomas, but for some authors, they should not be classified as meningiomas. Cytogenetic studies on meningioma demonstrate monosomy or partial deletion of chromosome 22 in 60% of these tumors. There have been few cytogenetic studies about meningeal hemangiopericytoma. We present here the results of cytogenetic studies and fluorescence in situ hybridization in six cases of meningeal hemangiopericytoma. In these tumours we have never found monosomy 22, but all six cases were hyperdiploid. These cytogenetic data might provide additional evidence to differenciate the meningeal hemangiopericytoma from the meningioma.

Adolescent↗
PubMed2002

Bone marrow cytogenetic complete remission achieved by interferon-alpha plus cytarabine ocfosfate therapy in a patient with chronic myelogenous leukemia during extramedullary blast crisis.

We report a case of chronic myelogenous leukemia (CML) in which the bone marrow achieved cytogenetic complete remission (CCR) achieved by treatment with interferon-alpha and oral cytarabine ocfosfate after extramedullary blast crisis. A 51-year-old Japanese man diagnosed with CML was treated with interferon-alpha. Two months later; lymph node swellings developed in his neck and inguinal regions. Lymph node biopsy revealed the infiltration of blast cells showing bcr-abl fusion signal by fluorescence in situ hybridization analysis. Bone marrow aspiration and cytogenetic analysis demonstrated that his bone marrow was still in the chronic phase, with minor cytogenetic response. Continuing interferon-alpha for 6 months in combination with oral cytarabine ocfosfate resulted in the disappearance of the neck lymph node swellings followed by CCR in the bone marrow. However, rapid reenlargement of the neck and inguinal lymph nodes was noted 2 months after CCR despite maintaining medullary remission with major cytogenetic response. Finally, medullary crisis was noted 13 months from the initial development of the extramedullary crisis. This case suggests that interferon-alpha plus cytarabine ocfosfate therapy may be of benefit in the treatment of extramedullary blast crisis of CML.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

Tumor cytogenetics revisited: comparative genomic hybridization and spectral karyotyping.

Fluorescence in situ hybridization techniques allow the visualization and localization of DNA target sequences on the chromosomal and cellular level and have evolved as exceedingly valuable tools in basic chromosome research and cytogenetic diagnostics. Recent advances in molecular cytogenetic approaches, namely comparative genomic hybridization and spectral karyotyping, now allow tumor genomes to be surveyed for chromosomal aberrations in a single experiment and permit identification of tumor-specific chromosomal aberrations with unprecedented accuracy. Comparative genomic hybridization utilizes the hybridization of differentially labeled tumor and reference DNA to generate a map of DNA copy number changes in tumor genomes. Comparative genomic hybridization is an ideal tool for analyzing chromosomal imbalances in archived tumor material and for examining possible correlations between these findings and tumor phenotypes. Spectral karyotyping is based on the simultaneous hybridization of differentially labeled chromosome painting probes (24 in human), followed by spectral imaging that allows the unique display of all human (and other species) chromosomes in different colors. Spectral karyotyping greatly facilitates the characterization of numerical and structural chromosomal aberrations, therefore improving karyotype analysis considerably. We review these new molecular cytogenetic concepts, describe applications of comparative genomic hybridization and spectral karyotyping for the visualization of chromosomal aberrations as they relate to human malignancies and animal models thereof, and provide evidence that fluorescence in situ hybridization has developed as a robust and reliable technique which justifies its translation to cytogenetic diagnostics.

Animals↗
PubMed2005

Cytogenetic findings in pediatric T-lymphoblastic lymphomas: one institution's experience and a review of the literature.

Cytogenetic analyses of lymphomas commonly reveal nonrandom chromosomal abnormalities, but there are relatively few reports in childhood lymphoblastic lymphoma (LL). We retrospectively reviewed G-banded karyotypic analyses performed at Arkansas Children's Hospital between 1990 and 2004. Six children (2 to 20 years old) had LL that presented as mediastinal or cervical masses and had a T-cell immunophenotype and clonal abnormalities. The cytogenetic findings in these 6 patients were as follows: 46,XX,-7,inv(9)(p11q12),der (12)t(7;12)(q11.2;p13),t(16;18)(p13.1;q21),+22 in patient 1; 47,XX,+9,del(9)(q11q22)x2 in patient 2; 72-119, XY,+X,+1,+1, inv(2) (p11q13),-3,+5,+6,+7,+10,-12,-16, -21,-21,-22,+mar in patient 3; 48,XY,+5,+20,t(7;9) (q32;q34) in patient 4; 47 approximately 48,XX,der(10)t(10;14)(q23; q11.2),+12, del(12)(p12)x2, -14,del(16)(q22q22),+?add (19)(p13.3) in patient 5; and 48 approximately 49,XY,+7,+8,t(11;19) (q23;p?13.3),+der(19)t(11;19)[cp20] in patient 6. Eleven chromosome breakpoints in 6 of our patients (7q11, 12p13, 16p13, 18q21, 9q11, 2p11, 2q13, 7q32, and 7q23) have been reported in other patients with acute lymphoblastic leukemia or LL and involved regions containing TEL, ABL, E2A, MLL, and T-cell receptor-alpha genes. A review of the cytogenetic findings of these and other cases of LL reveals that clonal aberrations are common and most frequently involve T-cell receptor gene regions. The aberrations show some features similar to those of acute lymphoblastic leukemia and are not unique to LL, thus furnishing additional evidence of the equivalence of these two diseases. The cytogenetic features of LL may be helpful in the diagnosis of pediatric lymphomas and undifferentiated neoplasms.

Adolescent↗
PubMed2005

[Tumor cytogenetics].

Cytogenetic analysis by classical chromosome banding, in combination with different fluorescence in situ hybridization (FISH) based methods, including comparative genomic hybridization and multicolour FISH, provides important information concerning the diagnosis, staging and prognosis of, as well as the planning of therapeutic intervention against, leukemias, malignant lymphomas and solid tumors, and may be helpful in monitoring the course of the disease. Cytogenetic methods identify primary chromosome anomalies that are causally involved in the emergence of the disease and its histopathological subtype, as well as secondary anomalies which have an effect upon the course of the disease and the responsiveness to therapy. Tumor cytogenetics is an independent discipline, and by no means only a diagnostic service for, or subdiscipline of, haematological, oncological and pathological fields. It is important, however, to point out that tumor cytogenetics is a cooperation-orientated and interdisciplinary science that deals with its own original questions in collaboration with clinicians, pathologists and molecular geneticists.

Cell Transformation, Neoplastic↗
PubMed1992

Correlation between cytogenetic and molecular analysis of t(14;18) in follicular lymphomas.

A comparison between cytogenetic and molecular results of t(14;18) has been performed in 12 patients with follicular lymphomas: five nodular and seven diffuse. Ten cases showed cytogenetic alterations with different markers, including a 14q+ in eight: in four it was the result of a t(14;18). Molecular analysis by Southern blotting with bcl2 probes from major and minor cluster regions, and PCR with primers from major and minor regions showed differences versus the cytogenetic results. The correlation found between cytogenetic and molecular results suggests other factors, such as geographical differences or different pathogenetic mechanisms, more than methodologic aspects, to explain the different frequencies of this marker among countries.

Adult↗
PubMed1994

Interrelationship between methodological choices and conceptual models in solid tumor cytogenetics.

Scientific methods and models are interdependent. That the techniques one uses determine which findings one gets, is evident. But equally important is the influence of our a priori expectations; they may cause us to choose inadvertently those methods that are most likely to yield results that appear to confirm an already preconceived picture of reality. The conceptual models and methods of solid tumor cytogenetics are to a large extent inherited from leukemia and lymphoma cytogenetics. We illustrate how this may bias the generation and interpretation of new findings, especially when carcinomas are investigated. These malignant epithelial tumors much more often harbor cytogenetically unrelated clones than do hematologic or mesenchymal neoplasms. Carcinoma cytogenetics is therefore extremely susceptible to selection differences, making the results heavily dependent on which sample is processed, how it is disaggregated, how and for how long the cells are cultured, and on how the analysis is performed and the results presented. This calls for more efforts to be directed toward establishing also the phenotypic nature of those cells that are being karyotyped. As one cannot yet quality-grade most clonal chromosome changes in any reliable manner, meaning that one cannot determine to what extent each aberration or each clone contributes to the neoplastic process, statements about the "true" karyotypes of tumor parenchymas should be viewed with suspicion. A complete carcinoma karyotype may be much more complex than extrapolations from the analysis of a few cells may lead one to believe.

Chromosomes, Human↗